Field of the Invention
The invention relates generally to systems and methods for extinguishing fires, and more particularly to a pallet rack storage system specially configured to suppress in-rack fires.
Description of Related Art
Articles stored in warehouses usually represent a significant capital investment in either raw, partially finished or finished good/inventory. In a warehouse, articles—sometimes palletized—are frequently stacked in multi-tiered rack arrays, which in turn are arranged in long rows. An unchecked fire can quickly destroy these valuable articles either by direct combustion, or collaterally be heat, smoke or water damage. Furthermore, articles stacked in rack arrays usually offer an abundant fuel source for a fire to grow and quickly propagate, making warehouse fires especially difficult to extinguish. It is therefore of great economic importance to rapidly contain fires in warehouses.
Fire containment is largely dependent on the rapid delivery of large quantities of water to the locus of the fire. That is to say, early stage fire containment in a warehouse storage setting is maximized when a lot of water is moved to the fire source as quickly as possible.
This objective is often frustrated in warehouse storage settings due to the fact that stacked or arranged rows of articles tend to make it difficult for water sprayed from an overhead fire sprinkler system to reach a fire starting deep inside a rack array near the floor. When articles are stacked or arranged in rows, narrow gaps between adjacent articles are formed. These narrow gaps are often called flues. There are transverse flues and, in cases, longitudinal flues. Transverse flues are formed in the gaps between adjacent articles in the same rack array, whereas longitudinal flues are created in the gap between two adjacent rack arrays arranged back-to-back. When a fire originates in or near the longitudinal flue, it is very difficult to reach the fire with water dispersed from an overhead fire sprinkler. The fire produces hot combustion gases that travel upwardly through the narrow flues like chimneys. When the escaping heat is sufficient to activate at least one nearby overhead fire sprinkler, water (or other fire suppressing liquid) will be discharged into the region. In order to be effective, the water must travel down the very same flues that the heat from the fire is rising through. The rising heat, concentrated within the narrow passageways of the flues will tend to vaporize the descending water spray unless sufficient quantities/densities of water can be applied to overpower the heat. The greatest success at fire suppression will be achieved when, at the initial stages of a fire, a maximum amount of water is applied to the flues nearest to the burning objects.
Furthermore, a surprisingly large percentage of water issuing from overhead sprinklers lands uselessly on the floor rather being usefully applied to combat a fire or wet surrounding objects in jeopardy. For water discharged from an overhead sprinkler, the initial point of water contact is, most commonly, over the uppermost surfaces of storage articles located on the highest elevation shelves located within the spinkler's reach, or wetting zone. Run-off water flows to the outer edges of these highly elevated storage articles and then cascades over the sides. A majority of the run-off water is expected to fall uselessly to the floor. Some small portion of the water is expected to migrate into the interior regions of the rack arrays, but is quickly evaporated by heat rising from the fire. As a result, in prior art fire suppression systems, a near-ground fire typically grows rapidly inside a rack array with little to no direct exposure to the sprayed water until the fire has grown large and powerful and set ablaze many levels of articles.
Understanding this problem, the prior art has taught to locate fire suppressing sprinkler systems inside of rack arrays, especially in the longitudinal flue area of rack arrays arranged back-to-back. In-rack sprinkler systems are notoriously expensive to install, and are prone to frequent damage from collisions as articles are frequently moved into and out of the rack arrays during normal warehousing activities. Furthermore, an in-rack system is usually installed in conjunction with a standard overhead fire sprinkler system, more than doubling the cost of a complete fire suppression system in a warehouse. And yet another drawback of in-rack systems is the constraint imposed on future remodeling efforts. That is to say, once an in-rack sprinkler systems is installed, a warehouse manager will be reluctant to rearrange the location of the affected rack arrays due to the integrated plumbing. Thus, in-rack sprinkler systems are not an attractive solution, but compared to the catastrophic prospect of fire in a warehouse are used with some frequency.
Another problem with in-rack sprinkler systems pertains to the distribution of water inside rack arrays. In particular, water forcefully discharged from a sprinkler head located deep inside (e.g., in a longitudinal flue) of a rack array will tend to explosively splash and ricochet, without much opportunity for thoughtful guided placement of water. Moreover, to protect the sprinkler heads from collision damage, it is common practice to intentionally shelter the plumbing and spray heads between the rack's structural horizontal beams. This sheltering of the spray heads severely compromised the spray pattern. Evidence of this concern can be seen, for example, in U.S. Pat. No. 5,636,755 issued Jun. 10, 1997. Here, the sprinkler heads are sheltered between specially shaped beams designed to channel water into the interior of the rack array. While this concept may have helped better distribute water from the in-rack system, still no benefit is provided to water discharged from overhead sprinklers whose run-off continues to cascades over the sides and fall uselessly to the floor. Furthermore, the requirement of specially shaped beams forecloses any opportunity for a retrofit solution universally adaptable to all major brands of racking systems.
There is a need in the art for an improved storage rack system that is compatible with overhead fire suppression systems and amenable to in-rack systems, and that will maximize rapid delivery of water to the fire-prone interior regions of a rack array.